Recently, the general trends in designing electronic devices towards high density, high performance, small size, light weight and portability. Moreover, with the increasing development of electronic industries, the electronic devices are gradually modularized. Electronic components (e.g. active components and passive components) are integrated into a power module, then install the power module on a motherboard or a system circuit board.
FIG. 1 schematically illustrates a package structure of a conventional power module. As shown in FIG. 1, the package structure 1 comprises a substrate 10, plural pins 11 and a housing 12. A process of fabricating the package structure 1 will be illustrated as follows. Firstly, active components (not shown), passive components (not shown) and pins 11 are soldered on a first surface 100 of the substrate 10. Then, the active components, the passive components and the pins 11 are connected with each other through bonding wires (not shown) by wire-bonding process. Moreover, the active components and the passive components on the first surface 100 of the substrate 10 are covered by the housing 12. The housing 12 has plural openings (not shown) corresponding to the pins 11. The pins 11 penetrate through the corresponding openings and partially expose outside the housing 12. Through the pins 11, the power module can be connected with an external circuit. The package structure 1 of the power module is produced.
Moreover, the housing 12 further comprises at least one rigid strut 121. The rigid strut 121 protrudes from the housing 12 and extends toward the first surface 100 of the substrate 10. When the first surface 100 of the substrate 10 is covered by housing 12, the rigid strut 121 is in contact with the first surface 100 of the substrate 10 to press the first surface 100 of the substrate 10. When the package structure 1 is mounted on another device with screw, the substrate 10 can maintain flat since a portion of the substrate 10 is pressed by the rigid strut 121. For example, a heat sink may be fixed on a second surface 101 of the substrate 10, wherein the second surface 101 is opposed to the first surface 100. In response to the pressing of the rigid strut 121, the substrate 10 will be in close contact with the heat sink and thus the heat dissipating efficiency of the package structure 1 is enhanced.
Although the arrangement of the rigid strut 121 can maintain the flat state of the substrate 10 by exerting pressing force upon the first surface 101, there are still some drawbacks. For example, since the rigid strut 121 is made of a rigid material, the substrate 10 is possibly damaged by the rigid strut 121 when the rigid strut 121 is in contact with the substrate 10. Moreover, since the rigid strut 121 is in contact with the first surface 100 of the substrate 10 when the first surface 100 of the substrate 10 is covered by the housing 12, the length of the rigid strut 121 should meet stringent requirements. That is, the rigid strut 121 should be precisely machined. Under this circumstance, it is difficult to fabricate the package structure 1.
Alternatively, the rigid struts can contact with the bonding wires that are disposed on the top surfaces of the electronic components and connected with the electrodes of the electronic components, and thus the rigid struts press the substrate indirectly. However, since the rigid struts are made of a rigid material and the structural strengths of the bonding wires and the electronic components are weak, the bonding wires or the electronic components are possibly damaged by the rigid struts. Under this circumstance, the power module cannot be easily fabricated.
Therefore, there is a need of providing an improved package structure in order to overcome the drawbacks mentioned above.